Thin film circuit devices, including transistors, diodes, and the like, are widely used in a variety of modern electronic devices, including integrated circuits, printed circuit boards, flat panel displays, smart cards, cell phones, and radio frequency identification (RFID) tags. Thin film circuit devices are typically formed by depositing, masking and etching a variety of conducting, semiconducting and insulating layers to form a thin film stack.
Typically, thin film transistors are based on inorganic semiconductor materials such as amorphous silicon or cadmium selenide. More recently, significant research and development efforts have been directed to the use of organic semiconductor materials to form thin film transistor circuitry.
Organic semiconductor materials offer a number of manufacturing advantages for transistor fabrication. In particular, organic semiconductor materials permit the fabrication of organic thin film transistors (OTFTs) on flexible substrates such as thin glass, polymeric or paper-based substrates. In addition, organic semiconductor materials can be formed using low-cost fabrication techniques such as printing, embossing or shadow masking. Although the performance characteristics of OTFTs have improved with continued research and development, device performance and stability continue to present challenges.